Universität Augsburg (2011)

Impact of Climate Change on the Water Availability in the Near East and the Upper Jordan River Catchment

Heckl Andreas

Titre : Impact of Climate Change on the Water Availability in the Near East and the Upper Jordan River Catchment

Auteur : Heckl Andreas

Université de soutenance : Universität Augsburg

Grade : Doktorgrade 2011

Résumé The Near East is a region with long-lasting political conflicts. At the same time it is one of the regions with the lowest water availability per capita in the world. This gives the Jordan River as a transboundary water resource a political relevance. Global climate change could aggravate the situation considerably. To enable sustainable water management within the affected countries scientific sound information about expected future climate change in the Eastern Mediterranean and its effects on the water availability is needed. For this purpose in this thesis joint regional climate-hydrology simulations are performed for the Eastern Mediterranean with a special focus on the hydrology on the Upper Jordan River basin. ECHAM4 data with the two SRES emission scenarios A2 and B2 are dynamically downscaled with the RCM MM5 transient for the period 1961 - 2099 and offline coupled to the mainly physically based distributed hydrological model WaSiM that was set up, calibrated, and validated for the Upper Jordan River. It was demonstrated that high resolution climate simulations with MM5 are able to reproduce the sharp transition of climate zones. The wetter conditions in the north and the coastal areas in contrast to the extremely dry area in the south and eastern areas as well as temperatures are simulated in sufficient accuracy. However, a seasonal bias in precipitation was investigated originating from the driving data of ECHAM4 and NCEP reanalysis that turned out to be serious, especially when the aim is to use the simulations for further impact analysis in terrestrial hydrology. Therefore, a bias correction with monthly scaling factors was performed in the forefront of the joint climate-hydrology simulations. The hydrological model WaSiM was successfully applied for the UJC including the innovative concept of representing the karst aquifer by a 2D-groundwater model for porous aquifers accompanied by an artificial bypass simulating the Dan spring. With this approach the water balance of the Upper Jordan River could be simulated satisfactorily. Thus, WaSiM turned out to be suitable for the UJC and showed plausible sensitive reactions on changes in the meteorological driving conditions based on climate simulations. When analyzing the simulation results the uncertainties of the modeling system itself have to be respected. With the use of two different emission scenarios another source of uncertainty, namely the unknown future anthropogenic greenhouse gas emissions, was tried to consider. Thus, an uncertainty margin of future climate conditions due to different greenhouse gas concentrations could be determined. In general it could be shown that global increase in greenhouse gas concentrations has a distinct impact to the region of the Jordan River. Simulation results show steadily rising temperatures in all seasons and all over the considered area while at the same time precipitation amounts are decreasing almost over the whole Jordan River region with one exception at the Egyptian coast at the southwestern part of the investigated area where small increasing rainfall amounts occur. Trend analysis of temperature assigns significant increase until 2050 of 1.3 – 1.7 K and until the end of the century of 3 K (scenario B2) and 3.7 K (scenario A2). Precipitation trends are until the middle of the century insignificant, although decreases of up to 20 % occur. This is due to the high variability of annual rainfall amounts in this region. For the end of the century reduction in rainfall ranging in most of the areas between 20 and >40 % is simulated. Trend tests for annual precipitation are highly significant for the period until 2099. The joint climate–hydrology simulations show a highly sensitive response to these modified atmospheric conditions. As actual evapotranspiration remains almost unchanged, simulated discharge in the UJC decreases until 2050 16.5 - 23.3 %, until the end of the century more than 40 %. Due to increased temperatures snow cover is likely to be lost as storage for spring and early summer discharge. Results of the joint climate–hydrology simulations let draw the conclusion that it is unlikely that changed climate conditions with warmer temperatures all over the year and reduced precipitation amounts resulting in significant reduction in annual discharge will stop discharge during summer since the karstic conditions serve as a big reservoir. However, water resources management faces most probably in the future strongly reduced water availability out of the Lake Kinneret fed by the Upper Jordan Rive